Apparatus for driving rivets using explosive charge

ABSTRACT

A RIVET DRIVING SYSTEM WHEREIN A MECHANICAL BLOW IS DELIVERED TO ONE END OF A RIVET BY AN AIR-DRIVEN HAMMER STRIKING AN IMPACT MEMBER WHICH ACTS AS A RIVET SET ENGAGING AND UPSETTING A HEAD ON THIS END OF THE RIVET. THE UNHEADED OPPOSITE END OF THE RIVET DELIVERS AN INITIAL SHOCK, AS THIS UPSETTING COMMENCES, AGAINST AN UPSETTING TOOL, OR SECOND RIVET SET, POSITIONED THEREAGAINST, WHICH IN TURN TRANSMITS A SHOCK TO AN EXPLOSIVE CHARGE. THE EXPLOSIVE CHARGE THEREBY EXPLODES, AND THE RESULTING GAS PRESSURE AND SHOCK DRIVES THE LAST-MENTIONED RIVET SET BACK TO FORM A HEAD ON THE CORRESPONDING END OF THE RIVET, WHILE THE FIRST MENTIONED RIVET SET IS STILL UPSETTING A HEAD ON THE FIRST MENTIONED END OF THE RIVET.

Feb. 16, 1971 J, c, w $Low ET Al. 3,562,893

A.PARATUS FOR DRIVING RIVETS USING EXPLOSI YE CHARGE Filed May 28, .968

2 Sheets-Sheet 1 3 mm 8 QM & y QNLil SW NW N WW4 r r 7 MC0 5% p 1M J2 Feb. 16, 1971 Q w s ow ETAL 3,562,893

APPARATUS FOR DRIVING RIVETS USING EXFLOSIVE CHARGE Filed May 28, 1968 2 Slwcts-Sheet Jana-'5 C l V/Msz on BY 40 0. ,4o4 w5 United States Patent Ofiice Patented Feb. 16, 1971 US. Cl. 29-24353 17 Claims ABSTRACT OF THE DISCLOSURE A rivet driving system wherein a mechanical blow is delivered to one end of a rivet by an air-driven hammer striking an impact member which acts as a rivet set engaging and upsetting a head on this end of the rivet. The unheaded opposite end of the rivet delivers an initial shock, as this upsetting commences, against an upsetting tool, or second rivet set, positioned thereagainst, which in turn transmits a shock to an explosive charge. The explosive charge thereby explodes, and the resulting gas pressure and shook drives the last-mentioned rivet set back to form a head on the corresponding end of the rivet, while the first mentioned rivet set is still upsetting a head on the first mentioned end of the rivet.

FIELD OF THE INVENTION This invention relates generally to apparatus for upsetting rivets, and more particularly to systems using the energy of a powder charge to upset a rivet.

BACKGROUND OF THE INVENTION The invention is useful in riveting generally, but has especial present application in the upsetting of titanium rivets now going into wide usage in the aircraft manufacturing industry. As is now known, the upsetting of titanium rivets, using a conventional pneumatic vibrating driver, presents some problems that have not been satisfactorily solved to date. A purpose of a primary feature of the present invention is to avoid vibratory drivers, and to substitute therefor a system using an air or other power hammer or means for transmitting or applying an impulse or impact to one end of the rivet, in conjunction with a powder charge, which is set oil by such impulse or impact, and instantly transmits an impact to the opposite end of the rivet, the two impacts thus timed forming heads on both ends of the rivet at the same time. Rivets having a self-contained powder charge which is exploded to upset a rivet are of course known.

SUMMARY OF THE INVENTION According to an illustrative practice of the invention, a first tool is provided which operates to deliver a blow from a massive air hammer through an interposed impact rivet set tool against one end of the rivet from one side of the plates to be riveted together, and this blow moves the initially unheaded opposite end of the rivet against an impact ram or rivet set in a second tool held by a second operator, or machine driver, on the opposite side of the plates. This second tool comprises a cylinder structure, an open end of which engages the plates over a protruding portion of the rivet shank. The rivet set on the second tool transmits a shock to a powder charge, backed up by a reaction piston, and so explodes the charge. The explosive gases in turn drive the rivet set back to upset the rivet shank, and this occurs while the air hammer and impact tool are still in engagement with, or are upsetting the first end of the rivet. The reaction piston travels in the cylinder under the force of the explosive gases, and is air-cushioned to arrest its travel. The upset rivet head formed by the second tool tightly fills the open end of the cylinder structure, and the recoil of this piston pulls the cylinder off the upset rivet. The end of the rivet impacted by the air-driven hammer may be of the initially unheaded or slug type, in which case the air hammer forms an upset head thereon. Alternatively, this end of the rivet may initially possess a head. The first tool mentioned hereinabove may substitute an explosive powder charge for the air hammer.

Present illustrative forms of the invention are shown in the following somewhat diagrammatic drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view of apparatus for upsetting a rivet in accordance with the invention;

FIG. 2 shows the parts in another position, after upsetting;

FIG. 3 is a diagrammatic illustration of explosive charges in or on a tape carrier;

FIG. 4 shows a modification;

FIG. 5 shows another modification; and

FIG. 6 shows another modification.

DESCRIPTION OF AN ILLUSTRATIVE EMBODIMENT There is shown in FIG. 1 a pair of overlapped plates '10 placed face to face, which have been bored for a rivet, and a rivet shank 11 is shown inserted therein, the rivet in this case being initially without a head at either end. The shank 11 is shown to protrude from both sides of the plates 10, and the protruding portions 1 1a and 11b are to be upset to form rivet heads. The invention as here shown for illustrative purposes is adapted for upsetting the portion 11a to form a common type of countersunk head, and for upsetting the portion 11b to form a special head using a known form of confining ring or collar, which facilities the upsetting operation with a hard material such as titanium. Thus, at 12 is designated a cylindrical ring, collar, or washer formed on its exterior side, i.e., the side towards the shank end, with an inwardly inclined frusto-conical surface 13, inside which the material of the rivet is squeezed in upsetting. Such a collar or ring is known in the art, as mentioned, and it is known to upset the portion 11b of the rivet by a pneumatic vibratory driver to spread the metal of the rivet to the outside diameter of the ring 12 and to force it into the space inside the frusto-conical surface '13.

The apparatus of the invention includes two tools A and B, used in conjunction as a system, the tool A, a mass impact driver, being on the lefthand side of plates 10 in the drawings, and the tool B, an internal explosion impact driver, on the righthand side thereof, and the two tools being applied to the protruding rivet portions 11a and 11b, respectively, in the arrangement clearly shown in FIG. 1.

The tool A comprises an air cylinder 14, with a counterbore 15 at the end facing the plates to be riveted. A heavy closure cap, plug or nosepiece 16 is screwed securely into the threaded outer extremity of counterbore 15. Slidably mounted in the cylinder 14 is a free piston or hammer 18, which can be driven to one end or the other of the cylinder 14 by air under pressure admitted either via conduit 19 leading to the lefthand end of the cylinder, or a conduit 20 leading to the righthand end of the cylinder, just at the juncture of the counterbore 15 with the bore of the cylinder 14. The conduit 20 and the port 20a through which it communicates into the interior of cylinder 14 must be of the large cross section so as to exhaust air rapidly from within the righthand end portion of the cylinder 14 when the hammer '18 is driven in the righthand direction. Port 20a may be enlarged circumferentially around the cylinder 14. The conduits 19 and 20 are controlled by a four-Way valve, designated diagrammatically at V1, and which will be understood to permit air under pressure arriving at an inlet 22 to the valve V1 from a suitable source of pressurized air, not shown, to be connected either to the conduit 19 or the conduit 20. As will be understood, when the air under pressure travels through the valve from inlet 22 to conduit 19, exhaust air from the cylinder is travelling through conduit 20 to low pressure outlet 24 (solid arrows in the drawing), and when air under pressure is connected to travel from inlet 22 to conduit 20, conduit 19 is connected through the valve to the low pressure outlet 24.

An impact rivet set or tool 29 includes a shank embodying in this illustrative embodiment a cylindrical body part 30 mounted for limited axial reciprocation in a concentric bore 32 extending axially and concentrically part way through closure plug 16, and having on its inner end an enlarged impact head 34. This shank further embodies an extremity extending beyond the body part 30, in the form of a coaxial, cylindrical upsetting tool element or punch 36 which is slidably received into the close fitting mouth or orifice of a divergent bore 38 extending coaxially into plug or closure 16. The bore 38 defines an upsetting die cavity 40, which opens through the exterior end face 42 on the closure 16. This face 42- is engageable with the plates 10, over the protruding portion 11a of the rivet, the rivet shank being received in the die cavity 40 and the bore '38 and being engaged and positioned axially by the end of punch 36. Exact ultimate positioning is governed by screwing closure 16 in or out of the threads in counterbore 15. The rivet shank itself laterally positions the tool A. A jam nut 16a screwed into the threaded part of closure 16 and tightened against the end of cylinder 14 holds the closure in adjusted position. Preferably, a steel ring spring 46 is mounted in a groove 48 formed in counterbore in the inner end of closure 16, and serves to receive the impact of the hammer 18 and impact member 29 and so protect the tool in the event that the hammer 18 is accidentally driven against head 34 when no rivet is in place in the tool to receive the shock. This member 46 has an angular strike face, as shown, and the impact head 34 has a chamfer at 34b to mate with it. These surfaces do not collide if a rivet is placed properly in the tool and is properly backed up.

In the present illustrative practice of the invention, the head to be formed on the lefthand end of the rivet shank is to be countersunk into the adjacent plate 10, and the rivet hole is accordingly countersunk on that side, as at 49. The other ri-vet head is to be, illustratively, of the high shear type using the previously mentioned collar 12.

The operation of the tool A, in the upsetting of the portion 11a of the rivet 11, is as follows: The tool is applied to the plates 10, over the protruding rivet shank, as shown in FIG. 1. The parts being in the position of FIG. 1, but with the air hammer 18 in the retracted position shown in dotted lines, air from the high pressure source travels from conduit 22 through valve V1 and conduit 19 to the end of the cylinder 14 at the left of the air hammer 18. The mass of the tool is sutficient that the operator can hold it against the work notwithstanding the force of reaction thereby experienced by the cylinder of the tool. The air hammer is thus accelerated toward the right to impact against the flange head 34 on the impact tool 29. Air initially within the cylinder 14 to the right of the air hammer 18 is freely exhausted through the large area conduit 20, the valve V1, which incidentally may be mounted directly on the side of the cylinder 14, and the large area exhaust 24. The drawing being largely diagrammatic in nature, no effort has been made to illustrate the large cross-sectional area of these parts, but it will be understood that the cross-sectional area must be great enough to permit free exhaust of the air initially Within the cylinder 14 so as not to materially impede the motion of the air hammer 18 in its stroke towards the impact tool 29. By this sequence of events, a large impact is transmitted through the impact tool 29 to the end portion 11a of the rivet. The rivet shank thereupon moves towards the right, and at the inception of this movement, it transmits and delivers a shock or blow against a rivet set 50 contained within the tool B, moving the end of rivet set 50 sharply against an explosive charge to set off the latter, as will next be described.

The tool B comprises a cylinder structure 60 with two offsets, providing an intermediate bore or cylinder 61, a reduced bore or cylinder 62 extending and opening through the reduced forward extension 64 of the cylinder 60 and a rearward enlarged counterbore or cylinder 66 in an enlarged cylinder portion 67 meeting the intermediate bore 61. The rearward end of the cylinder structure 60 has a strong closure cap 68 threaded into the counterbore 66. Opposite ends of the counterbore 66 are formed with ports 72 and 74, to which are connected conduits 76 and 78, respectively, connected through a four-way valve V2, only diagrammatically represented herein, to a high pressure air inlet 78 and a low pressure air outlet 80. It will be understood that the high pressure air inlet 78 can be connected by the four-way valve V2 to either end of the counterbore 66, while the other end of the latter is connected through the outlet 80 to low pressure, as represented by the full line and phantom line arrows in FIG. 1.

The aforementioned rivet set 50 has a cylindrical plunger, punch or upsetting element 82 slidable in bore 62, and which is engageable against the extremity of the protruding portion 11b of the rivet shank when the cylindrical tool B is positioned against the plates 10, with the tabular part 64 engaged over the rivet shank and over the collar 12 which has already been placed over the shank portion 11b. The rivet set 50 also includes a piston head '84 slidable in the lefthand portion of the intermediate bore 61.

Opposed to the piston 84 and slidable in the righthand portion of the bore 61, is a plunger 86 projecting from a large and massive piston 88 that is reciprocable in the cylinder bore 66, the members 86 and 88 comprising a massive reaction means 89 to oppose the explosive force of the powder charge, now to be described.

The powder charge comprises in this illustrative instance a pressed explosive disk 90 of powder or explosivematerial, capable of being set off by a shock or sharp impact. It may, if desired, have molded ridges, such as 91, which crush and explode instantly to facilitate the explosion, the burning of the main body of the disk progressing from the ridges where the explosion is initiated. Any form of powder charge capable of being set off 'by the arrival of the upsetting tool 36 at the end of the rivet shank 11 may of course be used.

In the loaded condition of the tool B (FIG. 1), the powder disk 90 is against one face of the piston 84, and the plunger 86 has been moved gently, without sharp impact, against the opposite face thereof. This has been accomplished by positioning the valve V2 to establish the connections shown in solid lines in FIG. 1, so that air is introduced into the cylinder bore 66 behind piston 88 through the restricted passage 74, and, acting at a regulated pressure of about the order of 15 p.s.i., has slowly moved the massive piston 88 toward the left in its cylinder bore. Towards the left-hand end of the travel of the piston 88 it uncovers a port 92, leading to at-.mos phere, thereby further reducing the pressure back of the piston 88, so that the piston 88 and plunger 86 move slowly and gently against the powder charge 90. The port 92 is made of such size in relation to the other factors involved that the piston 88 continues to move, though at reduced velocity, when the pressure falls somewhat as port 92 is opened.

The end of the intermediate cylinder bore 61 is fitted with a ring spring 92, adapted for protective engagement by the piston 84 in the event this piston should be driven forward by an explosive charge with no rivet in the tool. The piston 84 is chamfered as at 93 for engagement with the inclinded surface 94 on the ring spring 92.

The air hammer 18 of the tool A is large and massive and has a long stroke, so that it can be accelerated to a relatively high velocity and acquire large kinetic energy by the time it strikes the impact tool head 34. In this connection, the initial position of the hammer 18 will be understood to be at the lefthand end of the cylinder 14, as shown in phantom lines.

In the second tool B, the inertia or reaction member 89, comprised of the plunger 86 and piston 88, is preferably of a relatively large mass comparable, or substantially equal, to that of the air hammer 18. The impact members 29 and 50 are of much smaller mass.

To set a rivet in the plates '10, a rivet shank 11 is placed in a rivet hole therethrough, with its ends protruding on both sides, and a collar 12 is placed over one of these, in this case over the righthand protruding portion 11a. The tools A and B are held by two operators on opposite sides of the plates and the tool A is manipulated to engage its rivet receiving opening 40 over the rivet portion 11a, while the tool B is manipulated so as to engage the mouth of the bore 12 over the rivet portion 11b and the ring 12. The tools are at this time in the position of FIG. 1, with the exception that the air hammer 18 is at the retracted end of its power stroke and the reaction piston 89 is also in a retracted position, e.g., as represented in phantom lines in FIG. 1. They have been moved to these positions by manipulation of the valves V1 and V2 to deliver air under pressure to the proper ends of their cylinder bores.

The front face 42 of tool A and the front face 46 of tool B are held against the plates 10, and the operator for tool B manipulates valve V2 to move the piston 88 and its plunger 86, together with powder charge 90, (introduced as later described) gently forward until engagement is made with ram or rivet set 50, and the latter has engaged the rivet shank 111 and moved it against the punch 36 on impact member 29 in tool A. This positions impact rivet set member 29 against a fixed shoulder 34a at the junction of the bore of cylinder 14 with the counter-bore 15. It will be seen that the length of the rivet shank received in the tool A is adjustable by screwing end closure 16 in or out of the cylinder 14. The rivet shank should have a length such that, when its end portion 11a is received to the maximum depth in tool A as predetermined by the adjustment of member 16, its opposite end portion 111) will have a suitable length for the upsetting operation to be performed upon it in the tool B.

The valve V2 remaining in the position represented in full lines, the operator holding tool A shifts value V1 to the position shown in full lines. High pressure air is then delivered behind piston 18 (then in the phantom line position), and drives the piston with high velocity against the impact rivet set member 29. A slight shock impact movement, or shock wave, is thereby transmitted through the member 29 to the rivet shank 11, from there to the rivet set 50, and thence to the powder charge 90. The powder charge being backed up by the plunger 86 and massive piston 88 is thereby exploded, and the resulting high pressure gases act equally on the piston 84 of the relatively light rivet set 50 and the plunger 86 of the massive reaction piston 88. As a consequence, the rivet set 50 is driven powerfully against the rivet portion 11b.

The point of extreme interest and importance is that the massive air hammer 18, upon collision with the rivet set member 29 (full lines in FIG. 1), and upon delivering its blow thereagainst, then substantially instantly sets off the explosion of the powder charge. Note that this occurs before the air hammer 18 has transferred but very little of the kinetic energy to the rivet, and upsetting of the rivet portion 11a is still in the incipient stage. The air hammer 18 then decelerates and stops while giving up its remaining kinetic energy to upset the rivet portion 11a into the cavity 40 and the countersink 49. See FIG. 2.

Synchronized to occur during this same time interval is an upsetting of the rivet portion 11b under the force applied to the piston 84 of the rivet set 50 by the expanding gases generated by the explosion. Thus, while kinetic energy from the large air hammer 18 is being delivered to the rivet portion 11a to upset the latter and form a rivet head thereof, the explosive pressure of the detonated powder charge on the rivet set 5'0 creates a force driving the latter forwardly with high acceleration and velocity, so as to quickly develop a large amount of kinetic energy therein by the time it impacts against the rivet portion 11b. Thus, the rivet set 50 delivers kinetic energy to upset the rivet portion 11b into a rivet head 110 while air hammer 18 is delivering kinetic energy to the rivet portion 11a to upset the latter and thus form a rivet head 11 1 on the opposite end of the rivet (FIG. 2). The two effects thus tend toward an equalizing balance or offset.

The explosive pressure developed by the explosive charge not only exerts a force on the rivet set 50, but also an equal force on the plunger 86 projecting from massive piston 88. Because of the large mass of the piston 88, it is capable of a large force of reaction, permitting application of a large force to the rivet set 50. The plunger 86 and piston 88 move toward the right (FIG. 2), but with low acceleration because of their large mass. The velocity attained by the piston is thus low, and this movement of the piston 88 is cushioned and arrested by a body of air trapped and compressed in the right-hand end of cylinder 66-. The air escape port 92 is of course closed almost immediately by the piston 88. As the plunger 86 recedes rightward, it very shortly uncovers exhaust ports 96 in cylinder 61, permitting escape of the explosive gases. Recoil of the piston 88 is resisted by compression of air in the right-hand end of cylinder 66. A spring could conceivably be used for this purpose, if located in the right-hand end of the cylinder 66 between the end wall of the cylinder and a seat on the piston.

The recoil of the piston 88 can be further utilized to pull the tool B free of the upset rivet head 1 10, which may be tightly engaged in the surrounding bore 62.

It will be seen that a unique performance is achieved in that the working stroke of the air hammer 18, at the inception of the impact which it causes against one end of the rivet, automatically times and initiates the working stroke in the opposite direction of the explosive-driven rivet set 50, so that the latter does its work to form one rivet head while the air hammer is doing its work of forming a rivet head on the opposite end of the rivet. A unique performance takes place, in that the bucking effort against the rivet shank on the left-hand side of the plates 10 necessary to permit upsetting of a head on the right-hand side of said plates comes from the massive air hammer 18 and the kinetic energy thereof as the air hammer and rivet set tool 29 are upsetting a head on the rivet shank on the lefthand side of said plates. Also, the bucking effort against the rivet shank on the righthand side of the plates 10 comes first from the force of the explosion of the powder charge, backed up by the inertia of the massive piston 88.

The rivet heads produced by the process of the invention may require shaving at their outer ends, which can of course be done in a conventional manner.

The tool B can be loaded in various ways. A preferred practice in accordance with the invention is to provide a tape 100, of paper or thin plastic film, with the spaced, disc-shaped powder charges spaced therealong, as in FIG. 3, and in the general fashion now common in packaging of medical pellets. To load, the valve V2 of tool B is shifted to the phantom line position of FIG. 1, so as to deliver air under pressure to the left-hand end of cylinder 66, and so move piston 88 and plunger 86 toward the right sufficiently to uncover tape slots 98 formed in opposite sides of cylinder 61. These slots 98 may be in the plane of the exhaust ports 96. The tape 100 is then inserted in one slot 98 and continued out the other, so as to extend across the cylinder bore. The tape is positioned with a powder charge 90 substantially centered in the cylinder 61. Valve V2 is then shifted to introduce air to the right-hand end of cylinder 66, and the piston 88 and plunger 86 moved back slowly toward the left, as aforesaid. The moving plunger 86 shears the tape on both sides, and then transports the charge 90 down to a position against the piston of the rivet set (FIG. 1).

Other arrangements for locating the powder charge in the reloading process may of course be substituted.

A large number of modifications of the riveting system of the invention are possible, and various types of rivet heads may be formed.

for example, the rivet head formed of the rivet shank portion 11b may be of a conventional type rather than involve the use of the ring 12. In such case, a modified centering means for the tool B must be provided, and can comprise merely a concave, e.g., conical, centering depression 120 in the end of the rivet set, designated at 50a in FIG. 4.

In a further modification, the rivet shank may initially have a rivet head on one end. The tool A (see FIG. may generally be like tool A, but the impact member 29a, corresponding to member 29 of FIG. 1, has a shank 30a which projects through bore 32, continues through the front end of closure 16a, and has at its forward extremity a concave seat 110 for engaging the rivet head He on rivet shank 11f. When in engagement with the rivet head, the closure 1*6e does not quite engage the plates. Tool B can be exactly like that of FIG. 1, and the same type of rivet head can be formed, as represented.

In operation, the air hammer strikes the impact member 29a and causes the shank 30a thereof to deliver an impact against the head of the rivet. The rivet shank transmits a shock to the rivet set 50a, which sets off the explosion, and the rivet set is driven back to head the rivet by upsetting, as in the first described embodiment. The rivet transmits the necessary shock to the rivet set 50a partly, or wholly, by general deformation of the impacted structure toward the right, or partly, or wholly, by transmission of an elastic compressional or deformation wave longitudinally along the rivet shank, resulting in shock delivery against the powder charge.

FIG. 6 shows a modification for the tool A, incorporating a feature to accommodate its recoil. Reference numerals designating corresponding parts will be the same, but with addition of the suffix a in FIG. 6. In this case, the cylinder :14, corresponding generally to the cylinder 14 of FIG. 1, is made in two parts, a main cylinder part 130 for the air hammer 1-8' and an extension sleeve part 131 telescopically slidable on the front end of part 130.

The right-hand end portion of the cylinder 14' is annularly recessed at 133 to accommodate a coil compression spring 134 and back of this recess, the cylinder 14' has a raised land 156, immediately to the rear of which is a circumferential recess or groove 135. The sleeve 131 has a nose portion 136 which overhangs the extremity of the cylinder 14', and extends longitudinally therebeyond, being constructed to fulfill the functions of the right-hand extremity of the sleeve '14 in FIG. 1. Screwed into the opposite end of sleeve 131, and riding within the confines of the groove 135 in cylinder 14, is a stop ring 138 which holds the sleeve 131 assembled with the cylinder 14 when the sleeve :131 is released from its retracted position of FIG. 6, the front edge of the ring 138 at this time engaging the confronting groove edge 139 as a stop. Thus, prior to application to the work, the sleeve 131 is extended forwardly (to the right) from the position of FIG. 6 by the action of the spring 134, the stop ring limiting this engagement by abutting against stop shoulder 139. When the tool is applied to the work and pressed forwardly thereagainst, the sleeve 15a moves relatively to the right within the sleeve 131, which is stopped by the plates 10, and the parts assume the position of FIG. 6.

Operation is as follows: Assuming air hammer 18' to be initially at the left-hand end of cylinder 14', as air under pressure is admitted to the left-hand end of the cylinder, said hammer is accelerated toward the right, and a recoil reaction acts to the left on the cylinder. The operator may be holding the tool by the cylinder 14', and pressing it toward the right, to keep the nose face 42. against the plates 10, while the cylinder 14' recoils to the left. However, with some designs or masses of equipment, the recoil effect may overpower the operator effort, so that the cylinder 14' moves a short distance toward the left. If the occurs, the sleeve 131 will be held against this retraction by the spring 134, which, though extending in length somewhat owing to the recoil, nevertheless has sufiicient range of extension to maintain the sleeve 131 and the end closure or nose 16- with the end face 42' of the later pressed against the plates 10.

As a further modification of the invention, broadly, the tool A may employ an initial impact means of a nature other than a mass impact means, or hammer, and such means may, for example, comprise an explosive charge, set off for example by a hot wire, and whose explosive force delivers an initial impact, impulse, or shock wave that is transmitted through the rivet shank to set off the powder charge in the tool B.

It will be understood that the drawings and description are for illustrative purposes only, and that various changes in design structure and arrangement may be made within the scope of the invention and within the range of equivalents of the appended claims.

What is claimed is:

1. In a system for heading a rivet positioned in a hole through overlapping plates and having a portion at one end of said hole and a shank protruding from the opposite end of said hole, the combination of:

a mass-impact tool having therein movable impact means including a hammer and impact-delivering shank engageable with said rivet portion at said one end of said hole to effect shock impact movement of said rivet;

an internal explosion impact tool having therein a movable rivet set engageable against the end of said protruding rivet shank and adapted for upsetting thereof;

means in said internal explosion impact tool for positioning an explosive charge behind said rivet set to be detonated by shook movement of said rivet set owing to said shock impact movement of said rivet by said mass-impact tool; and

means for directing an explosive force from said detonation against said rivet set to drive said rivet set against and thereby upset said protruding rivet shank.

2. The subject mater of claim 1, wherein:

said mass-impact tool embodies an air cylinder, in-

cluding front end and rearward end closures;

said hammer comprises a massive free piston reciprocable therein;

said impact-delivering shank includes at one end an upsetting tool receivable in a passage through said front end closure and is adapted at its opposite end for striking by said free piston;

a source of pressurized air; and

means for selectively admitting pressurized air to either end of said air cylinder and releasing it from the other.

3. The subject matter of claim 2, wherein said passage through said front end closure is in the form of a die cavity to accommodate upsetting of said portion of said rivet at said one end of said hole through said plates.

4. In a system for heading a rivet positioned in a hole through overlapping plates and having a portion at one end of said hole and a shank protruding from the opposite end of said hole, the combination of:

a mass-impact tool having therein movable impact means including a hammer and an impact-delivering shank engageable with said rivet portion at said one end of said hole to effect shock impact movement of said rivet;

an internal explosion impact tool having therein a movable rivet set engageable against the end of said protruding rivet shank, embodying:

a cylinder structure including a front cylinder portion in which said rivet set is longitudinally slidable, an intermediate cylinder portion adapted to receive a rearward portion of said rivet set, and to receive an explosive charge adjacent and immediately to the rear of said rivet set, and a rearward cylinder portion to the rear of said intermediate cylinder portion;

a massive recoil piston slidable in said reaward cylinder portion;

a plunger in said intermediate cylinder portion projecting from and movable with said free piston, said plunger being engageable with said explosive charge to position it adjacent to said rivet set; and

said plunger and said recoil piston presenting a mass accelerated rearwardly in said cylinder structure in response to an explosion of said charge.

5. The subject matter of claim 4, including a pressure relief port closed by said plunger when said plunger is in engagement with said explosive charge and opened by said plunger for escape of explosive gases upon retraction of the plunger moving under the force of said gases.

6. The subject matter of claim 4, including means for decelerating said recoil piston in the last portion of its recoil movement in said cylinder structure.

7. The subject matter of claim 4, including a source of pressurized air, and means for selectively admitting pressurized air to either end portion of said rearward portion of said cylinder structure and releasing it from the other.

8. An internal explosion impact rivet setting tool comprising:

a cylinder structure including a front cylinder having an open front end adapted to receive a rivet shank and to define a rivet head formed by upsetting said shank, an intermediate cylinder extending rearwardly from said front cylinder, and a rearward cylinder, of larger diameter than said intermediate cylinder, extending rearwardly from said intermediate cylinder;

a rivet set having portions slidable in said forward and intermediate cylinders, said rivet set being engageable at its forward end with said rivet shank to upset the same and form a head thereon;

said intermediate piston being adapted to receive an explosive charge adjacent and immediately to the rear of said rivet set;

a massive recoil piston slidable in said rearward cylinder;

a plunger in said intermediate cylinder projecting from and movable with said free piston, said plunger being engageable with said explosive charge to position it adjacent to said rivet set; and

said plunger and rivet set presenting a mass accelerated rearwardly in said cylinder structure in response to an explosion of said charge.

9. The subject matter of claim 8, wherein said second cylinder is of a diameter intermediate the diameters of said forward and rearward cylinders, and

a piston head slidably fitting said second cylinder comprising the rearward end of said rivet set.

10. The subject matter of claim 9, including an exhaust port in a wall of said second cylinder uncovered by said plunger in movement of said plunger under the influence of an explosion of said charge.

11. The subject matter of claim 9, including means for decelerating said piston in the last portion of its recoil movement in said rearward cylinder.

12. The subject matter of claim 9, including a source of pressurized air, and

means for selectively admitting pressurized air to either end portion of said rearward cylinder and releasing it from the other.

13. The subject matter of claim 12, wherein said rearward cylinder has an air inlet port in the rearward end portion thereof for admitting said pressurized air to move said recoil piston and plunger toward and into a position of engagement with said charge, and there being an air exhaust port in the wall of said rearward cylinder uncovered when said plunger and piston are in said last mentioned position, and covered by said piston as it recoils from said last mentioned position to an explosion of said charge.

14. The subject matter of claim 8, including slot means in said intermediate cylinder rearward of said rivet set for feeding explosive charges into said cylinder.

15. A mass impact tool for striking a rivet, comprising:

an air cylinder including front end and rearward end closures;

a free piston slidable in said cylinder;

an impact-delivering shank including at one end an upsetting tool receivable in a passage through said front end closure and adapted at its other end for striking by said free piston;

means for accelerating said piston from a position at the rearward end of said cylinder into striking engagement with said shank;

said front end closure of said cylinder comprising a wall adjustable longitudinally of said cylinder, and including a front end face engageable with the adjacent member of a pair of plates to be riveted together.

16. A mass impact tool for striking a rivet, comprising:

an air cylinder including front end and rearward end closures;

a free piston slidable in said cylinder;

an impact-delivering shank including at one end an upsetting tool receivable in a passage through said front end closure and adapted at its other end for striking by said free piston;

means for accelerating said piston from a position at the rearward end of said cylinder into striking engagement with said shank;

the front end portion of said cylinder including a telescopically mounted sleeve;

spring means for urging said sleeve to an extended position;

stop means limiting the extension of said sleeve, and

said front end closure of said cylinder being mounted in said sleeve.

17. In a system for heading a rivet positioned in a hole through overlapping plates and having a portion at one end of said hole and a shank protruding from the opposite end of said hole, the combination of:

an impact delivering tool engageable with said rivet portion of said one end of said hole to effect shock impact movement of said rivet; an internal explosion impact tool having therein a movable rivet set engageable against the end of said protruding rivet shank and adapted for upsetting thereof;

means in said internal explosion impact tool for positioning an explosive charge behind said rivet set to be detonated by shock movement of said rivet set owing to said shock impact movement of said rivet by said mass-impact tool; and

means for directing an explosive force from said detol 1 a 1 2 nation against said rivet set to drive said rivet set 3,129,429 4/1964 Hilti 227-40 against and thereby upset said protruding rivet shank. 1/1970 H111 2275 1X References Cited GRANVILLE Y. CUSTER, 1a., Primary Examiner UNITED STATES PATENTS 5 US. Cl. X.R.

1,821,410 9/1931 Taylor 29243.53 29522; 72430; 22751 

